Periodic oxidation and reduction kiln



Oct. 21, 1958 M. KALAN 2,856,669 PERIODIC OXIDATION AND REDUCTION KILN Filed Sept. 17, 1954 5 Sheets-Sheet 1 M/CA/flEL Z 74 94/ IN V EN TOR.

BY mama Oct. 21, 195

Filed Sept. 17. 1954 M.KALAN PERIODIC OXIDATION AND REDUCTION KILN 5 Sheets-Sheet 2 Q-el can-Q HVVENTUR @Y ma Get. 21, 19-58 M. KALAN 2,856,669

PERIODIC OXIDATION AND REDUCTION KILN Filed Sept. 17. 1954 3 Sheets-Sheet 3 41/6 /454. I24; Aw

INVENTOR.

BY WZLTK walls so that most of the United States Patent Ofitice 2,856,669 PERIODIC OXIDATION AND REDUCTION KILN Michael Kalan, Van Nuys, Calif. Application September 17, 1954, Serial No. 456,675 5 Claims. (Cl. 25-132) This invention relates to a periodic oxidation and reduction kiln and more particularly to a kiln in which there are no muflies, bag-Walls or saggers utilized and the wares are heated by radiant heat from the insulating refractories and by the flame temperature directly.

In prior kilns which utilize mufiles, bag-walls or saggers, the refractories are formed of fire clay having a high specific heat and consequently a considerable time is required to heat up the kiln to the desired temperature and considerable time is also required to cool off the kiln. Because of this time lag, it has been found expedient to idle the prior kilns when they are not in use rather than to let the kilns completely cool off and, of course, such idling requires the use of unnecessary fuel. For instance, in prior kilns utilizing mutfies, the mufiles can only supply heat to the ware by conductivity through the muffies and a considerable time is required to heat up the muffles. Also, with the muffle type kiln, the volatiles cannot escape and are trapped inside the kiln to cause contamination of the ware. The mufiles, bag-Walls or saggers in these prior kilns are necessary to prevent contamination of the ware by the products of combustion since the wares are always composed of oxides of minerals, such as silica, aluminia, and calcium oxide which will react with the usual combustion products. Also, when such prior kilns were attempted to be used as reduction kilns, it was necessary to place within the kiln some material to take out the oxygen, such as camphor balls, or silicon carbide (SiC) so that the products of combustion would be carbon monoxide rather than carbon dioxide. By the pres ent invention, an open fire kiln is provided which eliminates the use of mufiles, bag-alls and saggers. An oxidizing condition is deliberately created within the kiln atmosphere by the introduction of excess air and the kiln is equipped with combustion chambers and fiues large enough to insure complete combustion with an excess of oxygen. Thus, the wares cannot be contaminated by the products of combustion. The use of upshot, open fire burners and insulating refractories of low specific heat and thermoconductivity makes it possible in the present invention to have radiant heat available immediately for the wares and also to utilize the fiame temperature. Since insulating refractories are utilized for the kiln walls, there is relatively little heat storage or heat loss through the sensible heat from the products of combustion are going directly to the ware by way of radiation and convection. A vent is provided in the top of the kiln where the impurities which have volatized from the ware can leave the kiln rather than remain in the kiln as in prior designs. In the kiln of this invention, the wares can be set openly on clay tile shelves or setters without danger of contamination. Because of the low specific heat of the insulating refractories, immediate radiant heat is obtained from the refractories and also from the flame temperature and the refractories will cool off quickly so that the operator can take advantage of rapid heating and cooling cycles in producing his wares and it is unnessary to idle the kiln in order to have it available 2,856,666 Patented Oct. 21, 1958 for quick utilization. By these rapid cycles, it is possible to freeze the glazes and obtain beautiful highlights and lusters.

When the kiln is used as an oxidation kiln, two sets of the kiln with only the reduction burners turned on. Also, both the reduction and oxidizing sets of burners can be used at the same time and the oxidizing burners will be used to control the increase in temperature of the reduction cycle if necometers in the gas supply line so that the operator can introduce a controlled reducing medium into the kiln at will and at any time and at any pressure. By keeping a record of draw trials, the operator can consistently duplicate the results of prior runs by keeping a chart of the pressure versus time for the various oxidizing and reduction sets of burners. In this way, beautiful copper reds and iron soledons can be reproduced at a later time.

During the time the kiln is used as an oxidizing kiln, it is possible to automatically control the temperature Within the kiln to cycle the temperature and maintain the temperature uniform between the top and bottom of the kiln throughout the cycle. In order to accomplish this result a thermocouple can be placed in the upper side wall and the lower side Wall of the kiln to continually measure the temperatures at these two positions and. a motor driven cam can be utilized to select the variations of temperature over a given period of time. By comparing the actual temperature in the kiln with the selected temperature, it is possible to control the gas supply to the two sets of oxidizing burners in order to have the actual temperature follow the selected temperature. Also, it is de sirable to have the temperature control switch from the top thermocouple to the lower thermocouple during short intervals so that the burners will be controlled alternately in accordance with the selected cycle. It is understood that the kiln of the present invention can. be made either in the form of a stationary periodic kiln or in the form of a periodic car shuttle or pusher type kihi. Thus, the present invention provides a novel kiln which can be utilized for both oxidation and reduction and the temperature and atmosphere in the kiln can be accurately and selectively controlled by the oxidizing and reducing burners.

It is therefore an object of the present invention to provide a periodic oxidation and reduction kiln having large enough combustion chambers and flues to insure complete combustion of the fuel in the oxidizing burners with an excess of oxygen and having reducing burners to introduce pure fuel into the kiln independently of the oxidizing burners.

Another object of the present invention is to utilize upshot, open fire oxidizing burne s and insulatingrefractories of low specific heat and thermoconductivity so that radiant heat is immediatelyavailable from the refractories and the ,fiame temperatures in order to quickly bring the kiln to a desired temperature prior to operation of the reducing burners.

Another object of the invention is to provide a kiln in which the oxidizing burners aresupplied with an excess of oxygen so th t t unnecesary. to'utilize mufiies, bagwalls or saggers in order to protect the ware from contamination by the products of combustion andin which the reducing burners introduce pure fuel directly into. the kiln. i i

Another object of the invention is to provide two sets of oxidizing burners, one directed up the sides of the kiln in order to heat the upper side walls and top of the kiln and a second directed toward the tile shelves holding the wares in order to heat the lower side walls andbottom of the kiln and. to providea set of reducing burners directed toward the tile shelves.

Another object of the invention is to. utilize oxidizing and reduction burners in which the fuel flow to each of the burners can be measured by a pressure gauge so that reproducible atmospheres can be obtained, to give any desired type of glaze.

Another objectof the invention is to provide a kiln which is flexible in its control of atmosphere bothfor oxidation and reduction and in which reduction atmospheres can be reproduced accurately.

These and other objects of the invention not specifically set forth above will become readily apparent from-the accompanying drawings and description in which:

Figure l is a perspective view of a stationary kiln incorporating the present invention showing the gas manifold for the various burners and the automatic temperature control box.

Figure 2 is a transverse vertical section along. line 2-l-2 of Figure 1 illustrating the sets ;of oxidizing and reducing burners and the tile setting for the wares,

Figure 3 is a horizontal section along line 3-3 of Figure 2 illustrating the placementof the piers, for the tile setting and the po'sitionof thelvarious burner ports in the floor of the kiln.

Figure 4 is a horizontal section along line 4-4 of Figure 2 showing the manifolds, for the" oxidizing and reduction burners and the pressure .gaugesand; solenoid valves for the manifolds.

Figure 5 isa vertical section along line S Sof Figure 2 illustrating the construction of. oneof the oxidizing burners and its position with respect tothe floor of the kiln,

Figure 6 is a vertical sectional view along line 6-.-6 of Figure 2 illustrating one of thereduction burners and the manner in which it passes through the floor of the kiln.

Figure 7 is a prospective. view of the automatic temperature control for controlling the solenoid valves in the inlets to the oxidizing burner.

Figure 8 is a schematic wiring circuit for the automatic temperature control unit.

Referring to Figure l, a kiln 10. of rectangular shape is illustrated having sides 1 1 and 12, rear wall 13, arched roof 14. and front door 15. All of these structures are constructed of layers 16 and 17 of insulating refractory fire brick of low specific heat so that it can be heated up and cooled off quickly by the kiln burners. Of course, the layer 16 must be resistant to higher temperature than layer 17. The floor 18 of the kiln is constructed of a fire brick of single composition and has openings for the various oxidizing and reductionburners utilized for the kiln, The floor and sides of the kiln can be supported by posts 19 at each corner which are seton transverse beams 20 at each end of the kiln. The door of the kiln is supported by hinges 21 and is closed by alatch Zlf.

diagram illustrating the The arrangement of the oxidizing and reduction burners underneath'floor 18 are illustrated in Figure 4 and the burners have a main manifold 22 connected to a gas supply through passage 23. A first set of oxidizing burners 24-43 are all connected to a rectangular manifold 34 which is supported by cross member 20' and is connected to the main manifold 22 through a passage 35. A second set of oxidizing burners 36-38 are connected to a straight manifold 40 which extends between the sides of manifolds 34 and the manifold 40 is connected to the main manifold 22 through a passage burners 42 and 43 are positioned above the manifold 40 and are connected to the main manifold 22 by a passage 44. A pilot light for each of the oxidizing burners is provided by a rectangular passage 45 which has a cross passage 46 so that all of the oxidizing burners are adjacent to either passage 45 or 46. The passage 45 is connected th e n ma i d 22 y Passa e n the pa sag 45. and 461 have burner openings '48 which provide a constantly. available flame for lighting the oxidizing burners. ss e on ns a a ve 9 r la in e amoun of pilot light needed to light the burners. The passages 35, 41 and44 have manual contr l valves 50., 51;and 52 respectively, to control the amount of gas supplied to the various burners and these passages also contain pressure gauges 53, 54; and 55, respectively, to indicate the amount of gas which is flowing to the various burners. In addition, solenoid valves 56 and 57 are positionedin passages 35 and 41, respectively, and are connected to the automatic temperature control through conduits 58 and 59, re pectively. The oxidizing burner 24-33, are all of'the upshot, open fire, inspirating type.

Referring to Figure 3, the floor 18 of the kiln has openings 60-69 positioned directly. over the burners 24-33, respectively, and also has openings 71-73 for the burners 3638, respectively. in addition, openings 74 and 75 are provided so that reduction burners. 42 and 43 can pass snugly through the floor 18'. The tile setting for the ware is composed of three tile sections 76, 77;and 78 which are supported on blocks 79 which arepositioned on the floor of the kiln as illustratedin Figure .3. Three blocks are spaced along each side of the kiln and two rows of two blocks each are positioned intermediate the side rows with the blocks staggered with respect to the blocks of the side rows. It Willbe seen that a-space 79' exists between the tile setting and the sides, back and front of the kiln, which space is sufficient for the openings 6il-69 to discharge the fuel'from'the burners 24-33 upwardly along the sides, back; a-nd -front of the kiln. Since the tile setting covers the openings; 7-143; for burners 36-38, respectively, openings will be dispersed along the bottom of the tile setting and will be discharged in a direction towards the sides, backandfront of'the kiln.

The construct-ion of oxidizing burner 36 is illustrated in Figure. 5 and it is understood that all of the oxidizing burners 24-33 and 3638 are of similar construction. The burner has a nozzle 86) which connects with an opening 81 in the manifold 40 and this nozzle supports tubular member 82 to which is secured a conical member 83. Air is drawn through member 83; and is mixed with fuel from the nozzle in'member 32; The nozzle 89 is threaded to support a plate 84 which can be moved,

relative to the bottom opening in the conical-member 83- in order to vary the primary air supplied to the burner, Also, a space 85 exists between the lower. surface of floor 18 and the upper end of member 82 so that secondary air can be; added to the fuel mixture leaving the burnerand entering the kiln. By "supplying the burners with primary air through member 83 and with secondary-air through space 85, sufficient air is mixed with the fuel in order to assure an excess of oxygen within the kiln. With such an excess of air, the flame temper,- ature from the oxidizing burners 24-33. occurs at the upper half and top of the kiln and serves to heat the in- 41. A pair of reduction the fuel discharged from these sulating refractory fire brick which is positioned in this Since it is desired to maintain a uniform temperature? upper part of the kiln. Also, the flame temperature of between the upper and lower parts of the kiln, it is necesburners 3638 will serve to heat the setting and floor sary to have the automatic control responsive to both of the kiln and the flame will be directed towards the of the thermocouples 88 and 90. For this purpose, a lower sides, front and back of the kiln to heat this region. relay switch is provided having arms 104 and 105 for By regulating the plate 84 of each oxidizing burner, an alternately opening and closing lines 58 and 59 to the oxidizing condition in the kiln is maintained by the invalves 56 and 57, respectively, and for alternately opentroduction of excess air and complete combustion of ing and closing lines 89 and 91 to thermocouples 88 the fuel will take place with an excess of oxygen S0 and 90, respectively. The switch arms are carried by that the ware will not be contaminated with combustion armature 106 and winding 107 is connected to battery products. By utilizing the upshot, open fire burners and source 108 through a movable switch arm 109, which insulating refractories of low specific heat and low is alternately moved into and out of contact with terthermo-conductivity, it is apparent that radiant heat will minal 110, Switch arm 109 carries a roller 111 which be immediately available from the refractories and from bears against a cam 112 which is rotated by a constant the flame temperature without the ware being contamispeed motor 113, and cam 112 is designed so that the nated. By adjusting the fuel supply and air supply f switch arm 109 will contact terminal 110 during half the two sets of oxidizing burners, the temperature in the the rotation of the cam when the roller 111 is on the upper half of the kiln controlled by burners 24-33 can high portion of the cam. When the cam roller follows he made equal to the temperature in the lower half which the lower surface of the cam, the switch arm 109 will is controlled by the burners 36-38 so that uniform tembe moved away from terminal 110 in order to break perature can be maintained throughout the kiln. Because the circuit to the solenoid winding 107, With the solef e oXCeSS of y n, it is unnecessary to use mufiles, noid winding 107 de-energized, the switch arms 104 and bag-Walls or Saggors in the kiln n because f he low 105 will assume the dotted line position of Figure 8 heat storage in the kiln, the kiln can operate in a rapid in order to complete the circuit from thermocouple 90 ycle to obtain quick f g f lazes and colors f 25 through line 91 to the millivolt meter 92 and to complete Ware t0 give g lustels- A Passage 86 is provided 1'11 the circuit from photocell 98 through line 59 to the the roof 14 0f the ln So t e volatiles resulting solenoid valve 57. When the solenoid winding is enerfrom the oxidation of the wares can pass o he gized by arm 109, the switch arms 104 and 105 assume rounding atmosphere and not contaminate the Were. the full line position of Figure 8 and arm 104 will con- Since the two sets of oxidizing burners can be adjusted t thermocouple 38 through li 89 t th illiv lt to give uniform temperature throughout the kiln and a meter 92 and will connect the photocell 98 through uniform change in temperature, it is possible to automatili 53 t h l n id valve 56, If th temperature cally con r l se tWO S of homers to P tho kiln measured by thermocouple 88 does not correspond to through any desired time-temperature oXl'datiofl Cycle the selected temperature, the photocell will be energized A control box 87 is positioned at the side 12 of the kiln to open valve 56 d increase h temperature i h and contains the automatic control apparatus which is u pe part f th kil and if th temperatupg ed Connected to a thermocouple 88 through line 39 and to by thermocouple 90 does not correspond to the selected thermocouple 90 through line 91. The thermocouple 8 temperature, the valve 57 will be opened to increase the i located in the pp P of side 12 and IheaSllroS t temperature in the lower part of the kiln. The cam 112 temperature in the upper p r ion of the k resulhng is rotated at a speed such that the switch arms 104 and from burners 24-63 while the thermocouple 90 is locate 105 will switch the automatic temperature control from in the lower part of Side 12 andmeasures the mp thermocouple 88 and valve 56 to thermocouple 90 and ture in the lower portion of the kiln resultlng from burnv l 57 every f seconds so th i i i ibl f ers- 36-38. As illus rated n igu e 7, e automatic any substantial temperature difference to exist between temperature control has a millivolt meter 92 of standard thermocouples 88 and 90. It has been found that if construction which moves a pointer 93 along tempe athe control is switched every thirty seconds or so that ture scale 94 of dial 95 to Indi ate h a tual p the kiln can be raised in temperature and a uniform temture at ei her thermocouple 88 r 90 n a n r p perature maintained between the lower and upper parts ently to be described. The pointer 9 arri s n opaq of the kiln. As previously discussed, the thermocouple shield 96 Wlllch is posltloned to P s be en & llght couple 90 and burners 36-38 control the temperature source 97 and a photocell 98 both of which are mounted in th upper part a d f f th kil hil th th on a pivoted arm The arm 99 also Carries a Pointer couple 90 and burners 36-38 control the temperature 100 for indicating the selected temperature on the scale t h floor and lower section f h kil 101 of the dial 95. The arm 99 is Conne ted o an a when the indicator 98 selects a different temperature having a roller Which Continually hears p from that existing in the kiln that the valves 56 and 57 the surface of cam 102, and the cam 102 is driven by are opened to supply more fuel. The automatic control a constant speed motor 103 sothat it rotates at a uniwill only be used to increase the temperature of the kiln form rate. The photocell 98 1s connected to solenoid and the hi 9 can h an extension 9 to prevent valve 56 through line 58 and to solenoid valve 57 through th t l ystem f perafing upon a decrease i line 59 in order to energize these alves- S Cam kiln temperature. Also, an automatic cut-off switch (not 102 is rotated, the arm 99 and the pointer 100 will be h can b used to disconnec moved to indicate the desired temperature at any given h end f h h i cycle-1's r time and the light source 97 and photocell 98 will move h illi lt t 92 ill n with the arm 99. in the event that the actual temperaature but the h ll 9 i ture being measured by the millivolt meter 92 does not correspond with the selected temperature indicated by oxidizin burner pointer 100, the shield 96 will not interrupt the light g S and the arrangement of the ther mocouples makes it possible to use the kiln as an oxidizts t hot 19 or htgj ifi g ig gggz 2: gg f i gf g fi mg kiln and raise its temperature in accordance with any valves 56 or 57 and s pply fuel to the associated burntime schedule by Selectmg the shape cam Th9 cooling of the kiln. The arrangement of two sets of crs. However, should the temperature indicated by the cooling cycle of the kiln can be the hand twO pointers correspond, then the shield 94 will intervalves and 51 for Sets of oxldlzmg burners mm the light path and the valves would remain closed and this control can be 1n accordance with the actual It is understood that the cam 102 can be of any desired mperature indicated by pointer 93. Of course, the

It is only shape to obtain the desired time-ternperature cycle. cooling could be controlled automatically by utilizing a cooling-means such as air jet-under control of a. proper cam.

Referringnow to the operation of the kiln as a re-.

duction kiln, the reducing-burners 42 and 43 both project snugly through openings 7,4; and 75, respectively, in the floor 18 in the. manner illustrated in Figure. 6 and these openings are small enough. that no air is drawn from beneath the kiln. The tip of each burner extends slightly above the upper surface. of the fioor so thatthe burners will supply pure. gas. to the interior-of the kiln at posi.- tions underneath the tilev settings. In. utilizing the kiln asa reduction kiln, itis mostconvenie-ntto conduct draw trials. with. the various. wares in order to obtain the beautiful copper reds. and. iron. calodons whichcan be. produced byv the kiln. In these draw trials, the oxidizing burners and the reduction burners are regulated by the handvalves SW52 and a record of the. pressures, as indicated by pressure gauges 53-55, against time is kept so. that the desired reducing atmospheres in the kiln can be duplicated. By regulating the valve. 52, pure gas as the reducing medium can be. introduced into the kiln at any time and at any pressure. The kiln can be first brought up to a desired temperature by the oxidizing burners and the reduction burners 42 and 43 can then be turned on to obtain a desired reduction atmosphere since the combustion of this pure gas depletes the oxygen supply within the kiln and also reduces the oxides of the ceramic ware. By regulating both the reduction burners and the oxidizing burners, both burners can be used at the same time and the temperature of the kiln can be increased by the Oxidizing burners if necessary. While the reduction process is endothermic in nature, it has been found that sufficient oxygen is available in the kiln after the oxidizing burners have been turned off and thereduction burners turned on, to produce some rise in temperature. Also, the temperature can be maintained uniform by utilizing both the reduction and oxidizing burners at the same time. The supply of pure fuel through the reducing burners produces carbon monoxide rather than carbon dioxide within the kiln since insuficient air is. available to produce carbon dioxide. It is understood that the pressure on the individual manifolds is an indication of the amount of fuel being supplied to each set of burners and that the temperature of the kiln will vary with regulation of pressure.

After the draw trials have been run and the desired time-pressure relationship has been determined, it is contemplated that the process could be automatically controlled by an automatic control system, such as previously described, to regulate the oxidizing and reduction burners. In. the usual reduction process, the kiln would bebroughttup to a desired temperature with the oxidizingburners before turning on the reduction burners.

By the-present invention, a periodic oxidation and reduction kiln is provided which. utilizes upshot, open fire oxidizing burners: to heat the kiln and an excess of oxygen is deliberately supplied to the kiln in order to maintain an oxidizing condition. The upshot, open fire burners are positioned within the kiln so that one set of burners will, heat the upper portion and the top of the kiln. while another set of burners will control the temperature in the lower portion and at thev floor of the kiln. By utilizing insulating refractories of low specific heat, fast temperature cycles can be obtained' The reduction burners for the kiln will supply pure fuel to the interior of. the kiln to create a reduction atmosphere within the kiln and the reduction cycle can be varied in any manner by using the reduction and oxidizing burners simultaneously or separately. The automatic control for the oxidizing burners makes itpossible to. increase the temperature. of the kiln on any desired time-temperature cycle.

It is apparent that the. kiln of the present invention providesa highly flexiblecontro1 of the kiln atmosphere for reduction, and there; is no contamination of the ware from the products of combustion nor from the inpingement of flame. By the combination of oxidizing and reduc-ing. burners, a controlled atmosphere is available at any temperature within the; operating temperature range of the kiln, and the kiln can be operated at will for either reduction oroxidation. Another important feature of the kilm is that refractory life is increased because of heating by flame temperature and radiation 1'?!" muities, bag-walls and saggers, and, thus, refractory maintenance is low. Because of the quick heating avail; able within the kiln, the kiln is very economical in. the fuel consumption since it need not be held at idle. temt e for long periods of time. in the present kiln, s are permitted to escape from the kiln. so that the v. res will not become contaminated as in priorkilns where the volatiles are trapped inside the kiln. The kiln can be constructed in various sizes and shapes and the arrangement of the oxidizing and reducing burners. can be varied to produce the desired heating of the kiln and the desired distribution of the reducing gas. Various types of insulating refractories can be utilized so long as they have a low specific heat. Various other modifications are contemplated by those skilled in the art without departing from the spirit and scope of the invention as hereinafter defined by the appended claims.

What is claimed is:

l. A periodic kiln for ceramic ware comprising a tile support for the ware spaced from the floor of said kiln, a first set of upshot inspirating burner positioned below the floor of said kiln, a first set of burner openings in said floor above said first set of burners and spaced around the sides of said kiln, a second set of upshot, inspirating burners positioned below the floor of said; kiln and a second set of openings in said floor above said second set of burners and located toward the center of said kiln from said first set of burner openings, said first set of burners serving to heat the the kiln and said second set of towards said support to heat the lower walls and. floor of the kiln, and a set of reduction burners extending into said kiln and passing snugly through openings in said floor located between said second set of openings to ob-. tain maximum turbulence of the pure fuel introduced to the kiln and maximum mixture of the fuel with the ware.

2. A periodic kiln asdefined in claim 1 wherein said first set of burner openings are located nearer the sides of the kiln than the edges of said support to cause the fuel discharge from said first openings to be directed upwardly in the kiln, and said second set of burner open; ings are positioned below said support to cause the fuel discharge from said second openings to pass horizontally between said support and said floor, said set of reduction burners also being positioned below said support.

3. A periodic kiln as defined in claim 2 wherein an air passage exists between the top of each burner of said first and second sets and the lower surface of the floor to permit secondary air to enter the burner opening for each burner, means for adjusting the primary air supply to each of said first and second sets, said primary and secondary air supplies being sufiicient to cause an excess of oxygen within the kiln when said set of reduction burners is inoperative.

4. A periodic kiln as defined in claim 1 wherein the walls, roof and floor of said kiln are constructed of insulating refractory material of low specific heat so. that the wares positioned on said support are heated directly by flame temperature and by radiation from said walls, roof and floor, the low heat storage of said refractory material permitting rapid heating and cooling of the wares.

5. A periodic kiln as defined in claim 1 havingmeans than by conduction through refractories, such as.

upper walls and roof of burners being directed 9 10' for regulating the pressure of the fuel supply to each set References Cited in the file of this patent of burners, and means for continually measuring said UNITED STATES PATENTS pressure, said regulating means being adjustable to select a desired reduction cycle and said measuring means pro- 407000 Eames July 1889 viding a record of fuel supply pressure during the cycle 5 5 0,911 Machlet 1925 period so that said cycle can be reproduced. 2456469 Thomas et a1 1948 2,495,561 Wilson Jan. 24, 1950 

